"We’re actually leaving in a couple days for South Africa, so I'll be with him," Hilton told PEOPLE at the launch party Friday for Madden’s new DCMA Collective store in Los Angeles.

But is the heiress really ready for life on a tour bus? "I'm just happy to be together, so no matter where we are, we'll have a great time," she says. After shows in Johannesburg and Cape Town, Good Charlotte heads to Europe and the U.K. before hitting the road in North America this summer in support of their album Good Morning Revival.

At the party, Madden said his favorite part of the clothing line he runs with twin brother Joel is the collaborative T-shirts they've done with celebrities including artist Shepherd Fairy, Oscar-winning rap group Three 6 Mafia, and musician Chris Robinson. Asked if he’d consider collaborating with Hilton, Madden tells PEOPLE: "I'd do anything she wanted. I'm a really easy guy to read. Everyone can tell I'm really happy. She's the most supportive [girlfriend], even as a friend, so supportive of everything I'm doing. And I try to be the same way for her."